We propose a method relying on structural measurements by small-angle scattering to quantitatively follow aggregation of nanoparticles (NPs) in concentrated colloidal assemblies or suspensions up to percolation, regardless of complex structure factors arising due to interactions. As experimental model system, the dispersion of silica NPs in a styrene-butadiene matrix has been analyzed by small-angle X-ray scattering and transmission electron microscopy (TEM), as a function of particle concentration. A reverse Monte Carlo analysis applied to the NP scattering compared favorably with TEM. By combining it with an aggregate recognition algorithm, series of representative real space structures and aggregation number distribution functions have been determined up to high concentrations, taking into account particle polydispersity. Our analysis demonstrates that the formation of large percolating aggregates on the scale of the simulation box (of linear dimension 1/qmin, here micron-sized) can be mapped onto the macroscopic percolation characterized by rheology. Our method is thus capable of determining aggregate structure in dense NP systems with strong – possibly unknown – interactions visible in scattering. It is hoped to be useful in many other colloidal systems, beyond the case of polymer nanocomposites exemplarily studied here.

Inspired by the path followed by Matthias Ballauff over the past 20 years, the development of thermosensitive core-shell microgel structures is reviewed. Different chemical approaches, from hard nanoparticle cores to double stimuli-responsive microgels have been devised and successfully implemented by many different groups. Some of the rich variety of these systems is presented, as well as some recent progress in structural analysis of such microstructures by small-angle scattering of neutrons or X-rays, including modeling approaches. In the last part, again following early work by the group of Matthias Ballauff, applications with particular emphasis on incorporation of catalytic nanoparticles inside core-shell structures – stabilizing the nanoparticles and granting external control over activity – will be discussed, as well as core-shell microgels at interfaces.

The radial density profile of deuterated poly(N,n-propyl acrylamide) shell monomers within core-shell microgels has been studied by small angle neutron scattering in order to shed light on the origin of their linear thermally-induced swelling. The poly(N-isopropyl methacrylamide) core monomers have been contrast-matched by the H2O/D2O solvent, and the intensity thus provides a direct measurement of the spatial distribution of the shell monomers. Straightforward modelling shows that their structure does not correspond to the expected picture of a well-defined external shell. A multi-shell model solved by a reverse Monte Carlo approach is then applied to extract the monomer density as a function of temperature and of the core crosslinking. It is found that most shell monomers fill the core at high temperatures approaching synthesis conditions of collapsed particles, forming only a dilute corona. As the core monomers tend to swell at lower temperatures, a skeleton of insoluble shell monomers hinders swelling, inducing the progressive linear thermoresponse.

Well-defined double hydrophilic block copolymers (DHBCs) of poly(ethylene glycol)-block-poly(N,N-diethyla-crylamide) (PEG-b-PDEAm) were synthesized via a reversible addition-fragmentation chain-transfer (RAFT) polymerization of N,N-diethylacrylamide (DEAm) using dithioester terminated PEG of different chain lengths as macro-chain transfer agents. Controlled molecular weight and narrow molecular weight distribution were achieved as proven by size exclusion chromatography (SEC). Cloud points (CP) were determined via turbidity measurements with ultraviolet-visible spectroscopy (UV-vis) and LCST by differential scanning micro-calori-metry (micro-DSC). They range from 32 to 40°C depending on the PDEAm length block and its concentration. Above the LCST, fluorescence spectroscopy and dynamic light scattering (DLS) demonstrated that the PEG-b-PDEAm copolymers self-organized into large aggregates. More interestingly, copolymers pre-aggregated at relatively high concentrations below the LCST.

Wheat gluten, one of the most complex viscoelastic protein networks in nature, is unique to get the specific texture of bread. Due to its complex protein composition, its insolubility in most solvents and the very high molar mass of half of the proteins (glutenin, the other half being gliadin), the architecture of the network is still not well understood. In this work, we have investigated model gluten protein extracts with contrasted compositions in glutenin and gliadin solubilized in a mild chaotropic solvent: ethanol/water (50/50 v/v). The samples display a liquid-liquid phase separation with an upper critical solution temperature that depends on the protein composition. The phase diagrams are consistent with the presence of supramolecular assemblies of proteins. To confirm the presence of these assemblies and fully characterize the objects dispersed in ethanol/water, we have used an asymmetrical flow field-flow fractionation (AsFlFFF) setup coupled with differential refractive index, multi-angle light scattering and dynamic light scattering detections to probe very dilute protein suspensions. We have identified three classes of objects, with distinctive molar mass, characteristic size and conformation: protein monomers, polymeric structures, and very loose protein assemblies with molar mass larger than 2.10 6 g/mol. A molecular characterization of the species by size exclusion chromatography in a denaturing solvent shows that polymers and assemblies are mainly composed of glutenin and ω-gliadin. The high content of ω-gliadin, devoid of cysteines, indicates the importance of non-covalent interactions involved in protein assemblies and might play a major role in gluten rheology

Free solution capillary-electrophoresis (CE) is a powerful separation technique for the characterization of diblock copolymers. In this work, four series of double-hydrophilic anionic and cationic block copolymers, namely, poly(acrylamide)-block-poly(acrylic acid) (PAM-b-PAA), poly(acrylamide)-block-poly((3-acrylamidopropyl)trimethylammonium chloride) (PAM-b-PAPTAC), poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA) and poly(poly(ethylene glycol) methyl ether acrylate)-block-poly(acrylic acid) (P(PEGA)-b-PAA), were synthesized by reversible additionfragmentation chain transfer (RAFT) polymerization and characterized by CE. The electrophoretic mobility distributions of the copolymers were transformed into distributions of composition ratio by introducing a retardation parameter, Xexp,, that represents the hydrodynamic drag retardation due to the neutral block of the copolymer. A linear correlation between Xexp and the ratio of the degrees of polymerization of each blocks was experimentally established and was consistent with the model of electrophoretic mobility of composite macromolecules with hydrodynamic coupling. Finally, the comparison of the distributions between the different copolymer families was significantly improved by considering the distributions in composition ratio compared to the electrophoretic mobility distributions, since it takes into account the differences in solvation, expansion and drag force according to the chemical nature of the blocks.

Biodegradable plastics appear as one promising means to help solving the increasing issue of environmental pollution by plastics. The present study aims at comparing the biodegradation mechanisms of two promising biodegradable plastics, PHBV Poly(3hydroxybutyrate-co-3-hydroxyvalerate) and PBSA Poly(butylene succinate-co-adipate) with the objective to provide a better understanding of the mechanisms involved and identify the most relevant indicators to follow biodegradation. For this purpose, the progress of the biodegradation process was monitored under controlled composting conditions at the laboratory scale at 58°C using several methodological approaches for evaluating polymer degradation. Indicators of the extent of material disappearance based on respirometry and